Effect of oral verapamil on ventricular irregularity in long-standing atrial fibrillation

In patients with chronic atrial fibrillation (AF), symptoms and cardiac function may be improved by regularizing the ventricular rhythm, even though the AF persists. This study concerned effects of i.v. and oral verapamil (V) on ventricular regularity. A regularizing effect was observed in 5 out of 10 patients after 0.15 mg of V/kg b.wt.i.v., but in only one patient after 80 mg of V By mouth. V in a dose of 240 mg by mouth resulted in ventricular regularity in 6 out of 10 other patients, 320 mg in a further 2 and 400 mg in the remaining 2 patients. Six patients were given chronic oral therapy in progressively increasing doses. Although ventricular regularity and symptom relief were obtained, intolerable side-effects precluded the evaluation of subjective long-term effects of this therapy in all but one patient. Further investigations, particularly concerning the pharmacokinetic mechanisms of V, are needed before the treatment can be recommended for patients with chronic AF.

Appearance of individual amino acid concentrations in arterial blood during steady-state infusions of different amino acid formulations to ICU patients in support of whole-body protein metabolism

BACKGROUND

Previous work has demonstrated a relationship between arterial amino acid concentrations and uptake of amino acids across peripheral tissues in healthy volunteers, as well as in chronically and acutely ill patients. The aim of the present study was to evaluate whether different amino acid profiles in commercially available amino acid formulations are translated into significantly different arterial amino acid concentrations presumably high enough to promote protein metabolism in intensive care unit (ICU) patients.

METHODS

Nonprotein calories (60% glucose: 40% lipid) were simultaneously and constantly infused over 72 hours. Different free amino acid solutions were infused at random to each patient for 24 hours in order to determine the appearance of steady-state arterial concentrations of individual amino acids. Basal metabolic and nutrition states were defined after a 12-hour infusion period with glucose in each patient. Healthy volunteers receiving a standardized oral meal served as reference subjects in measurements of venous amino acid concentrations after normal oral food intake.

RESULTS

The sum of all amino acids in arterial plasma increased significantly during steady-state infusions of all the free amino acid solutions vs basal state in ICU patients. Only glutamine, taurine, and tyrosine did not increase at all vs basal state during steady-state infusions of the 3 formulations. Alanine, arginine, citrulline, glycine, histidine, serine, methionine, phenylalanine, valine, and ornithine showed different concentration among the amino acid solutions during infusions. Healthy volunteers had significantly higher overall concentrations of amino acids in both fasted and fed state compared with ICU patients, which indicates that free amino acid solutions remain a limiting component in artificial nutrition to patients to promote arterial amino acid concentrations in the artificially fed state.

CONCLUSIONS

It appears important to continue further improvement of composition profile in solutions of free amino acids to promote adequate uptake across organ beds in promotion of protein balance in artificially nourished patients.

[Liver dialysis using MARS in acute hepatic failure. Promising results in a pilot setting]

Acute hepatic failure (AHF) is a life threatening condition with a high mortality rate. There is a need to buy time, either waiting for the liver to regenerate or waiting for urgent liver transplantation. Different modalities of "liver dialysis" have been used during the last decades but of no true success. However, a new technique has been developed called the MARS (Molecular Adsorbent Recycling System) built upon the same principle as haemodialysis but with the capacity to also remove albumin bound compounds thought to be toxic to the liver. This is a report of our ten first cases, all having AHF and considered for liver transplantation. The survival rate was 7/10 and of the 5 patients in need of 5 or more treatments all but one survived. In these cases the MARS-treatment seemed to have positive effects on the course and outcome of the disease but there are a need for controlled trials to clearly prove the benefit of the treatment.

[Liver transplantation--from experiment to routine care. Experiences from the first 500 liver transplantations in Gothenburg]

During a fifteen-year period, 500 liver transplantations have been performed at Sahlgrenska University Hospital in Göteborg. The results have improved, and factors influencing outcome are discussed. A one-year survival rate over 90% and a 5-year survival rate close to 80% can now be expected for most indications. Long-term complications as well as special problems occurring in different groups of recipients are discussed. New indications for liver transplantation such as liver metastasis of endocrine tumors are described. This article also describes our experience of in situ splitting and living-related liver transplantation as well as other innovations such as cavoportal hemitransposition and multivisceral transplantation.

[Guidelines for management of patients with acute pancreatitis]

During recent years new concepts and methods have been introduced in the management of acute pancreatitis. Severity and risk of complications show wide variation. Outcome is also dependent on the physician's experience and on his local resources. In this light the Swedish Society of Upper Abdominal Surgery has elaborated national guidelines for management. Attention is paid to diagnosis, severity assessment and etiology. Furthermore, guidelines are offered for treatment of mild and severe pancreatitis, as well as for the management of pseudocysts. The role of multidisciplinary intensive care specialist teams in the management of severe disease is emphasized. The guidelines are supported by the Swedish Society of Gastroenterology, the Swedish Society of Gastroenterology, the Swedish Society of Anesthesiology and Intensive Care and by experts from other Nordic countries.

The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system

The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 21.min-1) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (51.min-1) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 51.min-1 fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. Thirty minutes after the start of anaesthesia a control measurement was performed, after which a heat and moisture exchanger was inserted into the breathing system of the three groups randomly allocated to have one. Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l-1) but at a fresh gas flow of 51.min-1 there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.

Effects of fentanyl, nitrous oxide, or both, on baroreceptor reflex regulation in the cat

We have investigated the effects of fentanyl, nitrous oxide, or both, on carotid sinus baroreceptor reflexes in cats during basal chloralose anaesthesia. The bilaterally isolated carotid sinuses were perfused at prevailing systemic arterial pressure or at predetermined levels of pump-controlled pulsatile pressures of 50-200 mm Hg in steps of 25 mm Hg. Other major baroreceptor sites were denervated by bilateral vagotomy. Fentanyl decreased arterial pressure dose-dependently when the carotid sinuses were perfused at prevailing systemic arterial pressure and when the perfusion pressure was controlled artificially. High-dose fentanyl reduced significantly baroreceptor reflex responses in the sinus perfusion pressure range 50-125 mm Hg. Nitrous oxide increased arterial pressure in the carotid sinus perfusion range 75-125 mm Hg. There was no interaction between nitrous oxide and fentanyl for baroreceptor reflex responses. Our results indicated that baroreceptor reflexes, with and without nitrous oxide, were well preserved by moderate doses of fentanyl while high doses of fentanyl depressed baroreceptor reflexes.

Effects of desflurane on systemic, preportal and renal circulatory responses to infra-renal aortic cross-clamping in the pig

BACKGROUND

Different pharmacological approaches have been used in the control of cardiovascular responses to surgical infra-renal aortic occlusion (AXC). The aim of the present study was to explore the modulatory effects of desflurane (DES) on these responses.

METHODS

The study was performed in normoventilated chloralose-anesthetized pigs (n = 14). Measurements included cardiac output (CO), pulmonary vascular pressures, heart rate (HR) and mean arterial pressure proximal to the AXC site (MAPPROX). Renal arterial (QREN) and portal venous (QPORT) blood flows were measured ultrasonically. Systemic (SVR), preportal (RPORT) and renal (RREN) vascular resistances were derived. Sets of measurements were done a) prior to, b) during and c) 5 min after AXC. This was repeated, in a randomized fashion, at control (no DES) and with 4.9% and 9.8% DES, respectively.

RESULTS

DES decreased MAPPROX, CO, HR, SVR, RREN and RPORT. At control, AXC increased MAPPROX (+27%), SVR (+27%), QPORT (+14%), RPORT (+12%) and RREN (+43%). DES 4.9% did not change this response pattern. With 9.8% DES, the AXC-induced increases in MAPPROX (+17%) and SVR (+21%) were attenuated. At this stage, AXC caused no demonstrable changes in RREN or RPORT, while both QREN (+16%) and QPORT increased (+9%).

CONCLUSIONS

DES effectively controlled increases in proximal blood pressure during AXC. The increases in RREN and RPORT that were seen during AXC at control were inhibited by 9.8% DES. Consequently, at this DES dose, both QREN and QPORT increased during AXC.

Are the cardiovascular actions of dopamine altered by isoflurane?

Dopamine seems theoretically to be a rationale choice when adrenergic support is needed to counter undesired cardiovascular depressant effects of isoflurane. Although the cardiovascular effects of isoflurane (ISO) and exogenous dopamine (DA) are well documented, there are no reports on their pharmacological interaction. The effects of ISO 1.4% (MAC 1.0) on the cardiovascular response to exogenous DA were studied in dogs during chloralose anesthesia. Instrumentation included catheterizations of the femoral artery (for aortic pressures and heart rate, HR), the pulmonary artery (for thermodilution cardiac output, CO, and pulmonary arterial pressures) and the left ventricle (for tip-manometer measured left ventricular end-diastolic pressure, LVEDP). ISO per se decreased HR (-16%), mean arterial pressure (MAP; -33%), CO (-29%), left ventricular dP/dt (LV dP/dt; -51%), and increased pulmonary artery occlusion (PAOP; +64%) and LVEDP (+28%). Prior to ISO, DA increased MAP, CO stroke volume (SV), LV dP/dt and LV dP/dt/SAP (systolic arterial pressure) at the dose 10 micrograms.kg-1.min-1. At the dose 20 micrograms.kg-1.min-1 DA, besides these effects, increased PAOP and mean pulmonary artery pressure (MPAP). During ISO, DA at the dose 10 micrograms.kg-1.min-1 restored MAP, CO, and SV to pre-ISO control levels, while LV dP/dt was increased to +96% above the pre-ISO control level. At the dose 20 micrograms.kg-1.min-1, DA increased MAP (+33%), LV dP/dt (+172%), PAOP (+132%) and MPAP (+50%) above pre-ISO control levels. The cardiac effects of DA were similar to when it was given alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Complement activation during liver transplantation

Twelve patients with end-stage liver disease undergoing liver transplantation were studied regarding complement activation and formation of anaphylatoxins (C3a and C5a) and terminal C5b-9 complement complexes (TCC) after reperfusion of the grafted liver. Blood samples for complement variables (C1INH, C3, C4, C5, C3a, C5a, and TCC) were drawn preoperatively, before the anhepatic phase, 1 min before, and 2, 15, and 60 min after the start of reperfusion of the grafted liver. Activation of complement was observed during the operation. The C1INH, C3, C4, and C5 plasma concentrations decreased during the entire operation while the anaphylatoxin C3a and the terminal C5b-9 complement complex increased after the reperfusion of the grafted liver. Activation of complement with the formation of biologically active substances like anaphylatoxins and terminal C5b-9 complement complexes may be one explanation for circulatory complications often seen in patients undergoing orthotopic liver transplantation.

The effects of propofol, methohexitone and isoflurane on the baroreceptor reflex in the cat

The effects of propofol (P), methohexitone (M) and isoflurane (I) on the baroreceptor reflex were studied in a cat model in which the blood pressure in a bilateral isolated carotid sinus preparation was artificially varied between 50-200 mmHg. The influence from aortic and cardiopulmonary baroreceptors was excluded by vagotomy. With basal chloralose anaesthesia as control, the investigated anaesthetics were used in doses corresponding to MAC 0.5 and 1.0. The maximum change in systemic mean arterial pressure (MAP) and heart rate (HR) following a defined increase in carotid sinus pressure was used as an index of baroreceptor reflex sensitivity. Compared to control, M and I anaesthesia were associated with significant depression of baroreceptor reflex sensitivity at the high dose (corresponding to MAC 1.0), and during I anaesthesia also at the low dose (MAC 0.5). The baroreceptor reflex sensitivity was maintained during propofol anaesthesia. The carotid sinus pressure interval at which the maximum changes in MAP could be elicited, was significantly higher during M than during P. This indicates resetting of the baroreflex.

Isolated hyperthermic liver perfusion with cytostatic-containing perfusate activates the complement cascade

Eight patients with advanced liver malignancy undergoing isolated hyperthermic liver perfusion with melphalan and cisplatin were studied with regard to complement activation and formation of anaphylatoxins (C3a and C5a) and terminal C5b-9 complement complexes (TCCs). Blood samples for complement variables (C1-INH, C3, C4, C5, C3a, C5a and TCCs) were taken before surgery, 1 min before the start of perfusion, 1, 2 and 3 h after the start of perfusion, and 24 h after operation. Samples were drawn from the perfusate 1 h after the start of perfusion. Activation of complement was observed during perfusion. Raised plasma concentrations of C3a and TCCs were recorded and high levels of C3a and TCCs were found in the perfusate. In vitro tests indicated that melphalan and cisplatin may activate complement. This activation occurred at 37 and 42 degrees C but was more pronounced at 42 degrees C.

Inspiratory to end-tidal oxygen difference during nitrous oxide anaesthesia

In order to evaluate the value of the inspiratory to end-tidal oxygen concentration difference (Io2-E'o2) as a monitor during general anaesthesia, we studied 40 orthopaedic patients allocated randomly to four groups: anaesthesia with enflurane or isoflurane in nitrous oxide with either spontaneous or controlled ventilation. (Io2-E'o2) followed an asymptotically increasing curve because of decreasing uptake of nitrous oxide. At 1 h, (Io2-E'o2) approached the end-tidal carbon dioxide concentration (E'o2). During spontaneous ventilation, (Io2-E'o2) correlated best with E'co2. During controlled ventilation, there was a negative correlation between (Io2-E'o2) and nitrous oxide uptake rate. Changes in oxygen uptake rate were reflected in (Io2-E'o2), provided that the total ventilation volume was constant and the nitrous oxide uptake rate approached steady state conditions.

Local vascular effects of isoflurane during regional intestinal hypothermia in cats

The influence of isoflurane on intestinal blood flow (IBF) during regional intestinal hypothermia (28 degrees C intraluminal temperature) was investigated in cats (n = 12) during basal chloralose-nitrous oxide anesthesia. A jejunal segment, which was dissected free in situ and intermittently cooled in a saline bath, was perfused via an extracorporeal arterial circuit which included a roller pump and a variable arterio-venous shunt. Intestinal perfusion pressures were controlled by adjusting the shunt flow. IBF was measured (optical drop-recording) during regional normothermia and hypothermia. The protocol included steady-state recordings at defined perfusion pressures (50, 75, 100, 125 and 150 mmHg in a randomized order; 6.7, 10.0, 13.3, 16.7 and 20.0 kPa, respectively) with and without the addition of 0.7% isoflurane. During normothermia, IBF levels were higher during isoflurane anesthesia than during basal chloralose anesthesia. Regional intestinal hypothermia induced no significant changes in IBF during basal chloralose anesthesia. However, the intestinal vasodilator effects of isoflurane, as shown during normothermia, were efficiently countered by regional cooling of the intestinal segment to 28 degrees C. Accordingly, hypothermia IBF levels were similar, regardless of whether isoflurane was administered or not. This could have an impact on the choice of anesthetic techniques.

Effects of thoracic epidural anesthesia and adrenoceptor blockade on the cardiovascular response to dopamine in the dog

The cardiovascular effects of dopamine are different before and during thoracic epidural anesthesia (TEA). To evaluate underlying adrenoceptor-mediated mechanisms, dopamine effects were investigated in nine chloralose-anesthetized dogs. The circulatory response to dopamine (0-40 micrograms.kg-1.min-1) was studied before and during TEA, and during TEA after introducing the alpha 1-antagonist prazosin (0.3 mg.kg-1), the alpha 2-antagonist rauwolscine (0.3 mg.kg-1), and the beta 1-antagonist metoprolol (0.5 mg.kg-1). TEA decreased mean arterial pressure (MAP) by 29%, cardiac output (CO) by 36%, heart rate (HR) by 27%, and the maximum rate of change of left ventricular pressure (LVdP/dt) by 52%. Systemic vascular resistance, pulmonary vascular resistance and mean pulmonary artery pressure (MPAP) remained unaltered by TEA. Dopamine-induced increases in MAP and HR were augmented by TEA. Both MAP and LVdP/dt increased above pre-TEA levels at 10 micrograms.kg-1.min-1. Prazosin attenuated the increases in MAP and MPAP by dopamine. Adding rauwolscine almost abolished the dopamine response in MAP and MPAP. Metoprolol almost eliminated the dopamine effects on CO and LVdP/dt. Only minor alterations in cardiac filling pressures were observed during the study. Plasma norepinephrine (NE) concentration was lower during than before TEA at corresponding dopamine infusion rates. NE was reduced by the beta 1-blockade. During TEA, the plasma dopamine levels were generally higher, and they were further increased by adding beta 1-blockade. In conclusion, myocardial contractility and arterial pressure were restored to pre-TEA values by dopamine at 5-10 micrograms.kg-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic gas exchange during aortocoronary bypass surgery using a double pump system and mechanical ventilation. A comparison between indirect calorimetry and invasive blood gas measurements using Fick's principle

Oxygen uptake and carbon dioxide excretion during aorto-coronary bypass surgery were studied in seven patients by indirect calorimetry and compared to blood-gas based measurements. Medium-high dose fentanyl, droperidol and midazolam were used for maintaining anaesthesia. During the period of extracorporeal circulation no external oxygenator was used. Circulation was maintained by two pumps by-passing the left and right heart respectively and the patient's lungs were ventilated with O2/N2 using a Servo 900C ventilator. For indirect calorimetric measurements gas concentrations were analysed by Beckman instruments and gas volumes were measured by the Servo 900C ventilator. Oxygen uptake and carbon dioxide excretion decreased by 31% and 39%, respectively. For invasive measurements during extracorporeal circulation, arterial and venous blood gases and pump flow were used. Using pump flow instead of cardiac output when calculating oxygen uptake circumvented errors in thermodilution measurements. There was a good correlation (r = 0.88) between the invasive and the indirect calorimetric measurements. Further, there was a good correlation between naso-pharyngeal temperature and indirect calorimetric measurements of oxygen uptake (r = 0.87).

Metabolic gas exchange during nitrous oxide anaesthesia with controlled ventilation

A system for metabolic gas exchange has been used during nitrous oxide-opioid anaesthesia incorporating a Servo Ventilator 900 C and external analysers for oxygen and carbon dioxide. Oxygen consumption and carbon dioxide excretion were calculated as differences in content between inspired and expired minute ventilation. Nitrous oxide uptake was calculated similarly, assuming it was the only other gas present in addition to oxygen and carbon dioxide. The mean value for oxygen consumption was 3.25 ml kg-1 min-1, declining by 8% during the 2 h of anaesthesia. The formula for the best fit curve of nitrous oxide uptake was 18.3 . t-0.48 ml kg-1 min-1 when FIN2O was 0.7. To simplify measurement procedures and avoid measurements of expiratory volume, we also calculated metabolic gas exchange when expiratory minute ventilation was expressed as a function of inspiratory minute volume and nitrous oxide uptake. The latter value was obtained from the overall best fit curve for nitrous oxide uptake.

Effects of isoflurane on feline intestinal blood flow during hemorrhage-induced hypovolemia

The influence of isoflurane on intestinal reflex vasoconstriction during hemorrhage was investigated in cats (n = 10) during basal chloralose-nitrous oxide anesthesia. Intestinal blood flow (IBF) was studied in a model with controllable intestinal perfusion pressures to exclude local myogenic vascular responses related to changes in intraluminal pressure. A jejunal segment, which was dissected free in situ, was perfused via an extracorporeal arterial circuit which included a roller pump and a variable arterio-venous shunt. Intestinal perfusion pressure was controlled by adjusting the shunt flow. IBF was measured (optical drop-recording) before and after hemorrhage (8% of estimated blood volume). The protocol included steady-state recordings at defined perfusion pressures (50, 75, 100, 125 and 150 mmHg in a randomized order; 6.7, 10.0, 13.3, 16.7 and 20.0 kPa, respectively) with and without the addition of 0.7% (MAC 1.0) isoflurane. IBF levels were consistently higher during isoflurane anesthesia than during basal chloralose anesthesia in the perfusion pressure range 75-150 mmHg (10.0-20.0 kPa). During basal anesthesia, a hemorrhage-induced decrease in IBF was demonstrated throughout the perfusion pressure range 50 to 150 mmHg (6.7-20.0 kPa). The magnitude of the hemorrhage-induced decrease in IBF was not significantly influenced by the addition of isoflurane. Thus, IBF, following hemorrhage, was significantly higher during isoflurane anesthesia than during basal chloralose anesthesia at perfusion pressures 50, 100, 125 and 150 mmHg (6.7, 13.3, 16.7 and 20.0 kPa).

Whole body gas exchange: amino acid and lactate clearance as indicators of initial and early allograft viability in liver transplantation

A method for the rapid assessment of liver allograft circulation and function after liver transplantation is described. In 12 patients undergoing liver transplantation continuous recording of whole body energy production was made on the basis of gas exchange measurements during the surgical procedure. Oxygen consumption decreased rapidly by 25% when the blood supply to the native liver was interrupted. After the anhepatic period, there was a sharp increase of oxygen consumption with successful reperfusion of the allograft. Carbon dioxide production fell by 14% and returned to preanhepatic values after successful declamping. In two cases with suboptimal reperfusion the return of gas exchange values was slow and incomplete. Results from the studies of whole body energy production were compared with biochemical measurements. No significant accumulation of amino acids occurred during the anhepatic period, but in the two patients with incomplete revascularization, clearance of amino acids, after the anhepatic phase, was impaired and plasma amino acids accumulated. The same pattern was found for plasma lactate levels. By the techniques described in this article, rapid and reliable assessment of initial and early graft function in hepatic transplantation is possible. This is of great value for the intraoperative and early postoperative assessment and planning of surgical and anesthesiologic strategies.

Effects of halothane, enflurane, and isoflurane on coronary vascular tone, myocardial performance, and oxygen consumption during controlled changes in aortic and left atrial pressure. Studies on isolated working rat hearts in vitro

The effects of equi-anesthetic concentrations of halothane (HAL, n = 11), enflurane (ENF, n = 11) and isoflurane (ISO, n = 10) on cardiac function were studied and compared with a control group (n = 12) in isolated paced rat hearts by means of an antegrade heart perfusion technique. Left atrial pressure (LAP) and mean aortic pressure (MAP) could be altered independently of each other, and aortic flow, coronary flow (CF), and po2 in venous coronary effluent were continuously recorded. Stroke volume (SV), myocardial oxygen consumption (MVO2), and myocardial oxygen extraction were calculated: 1) MAP was altered from 60 to 120 mmHg at a constant LAP (7.5 mmHg), and 2) LAP was varied from 4 to 12.5 mmHg at a constant MAP (80 mmHg). Left ventricular function curves (LVFC) were constructed and the maximal SV (SVmax) was obtained. The LAP needed to perform 75% of the maximal SV (LAP0.75) was estimated to assess the effect of the anesthetics on diastolic function. HAL ENF and ISO decreased SVmax significantly compared to control. This decrease was more pronounced for HAL (41%) compared to both ENF (26%) and ISO (26%). Accordingly, SV, at various levels of MAP, at a constant LAP, was significantly lower for HAL than for both ENF and ISO, while there was no significant difference between the latter two. None of the anesthetics shifted the LVFC to the right, i.e., did not affect diastolic properties. HAL induced the most pronounced decrease in MVO2, while there was no significant difference between ENF and ISO in this respect. Coronary flow (CF), at controlled perfusion pressures, decreased significantly with HAL but not with ENF or ISO compared to control. CF was significantly higher with ISO compared to both ENF and HAL. HAL and ISO, but not ENF, decreased myocardial oxygen extraction significantly compared to control and, thus, increased the myocardial oxygen supply-to-demand ratio.

Propofol vs thiopentone as anaesthetic agents for short operative procedures

In a randomized open study, 120 healthy female patients were included. For short gynaecological procedures they were anaesthetized with either propofol 2.5 mg X kg-1 (n = 60) or thiopentone 5 mg X kg-1 (n = 60) in combination with nitrous oxide/oxygen (67%/33%). Supplementary doses of propofol (10-20 mg) or thiopentone (25-50 mg) were given when necessary during the procedure. Induction characteristics for propofol and thiopentone 1 min after start of induction were similar. Propofol seemed to have a more depressant effect than thiopentone on the circulatory response to anaesthesia. Recovery times from the end of the operative procedure until the patients opened their eyes on command and were orientated were shorter in the propofol patients compared to the thiopentone patients. In the propofol group, patients recalled discomfort on injection more often than patients anaesthetized with thiopentone. Otherwise, the side-effects were similar in both groups. We conclude that propofol is similar to thiopentone in its anaesthetic qualities during induction and maintenance of short anaesthetic procedures. Propofol was associated with a more rapid emergence from anaesthesia than thiopentone.

Successful vasoconstrictor therapy of anaphylactoid reactions during induction of anaesthesia. A report of two cases

Anaphylactoid reactions were evoked during intravenous induction of anaesthesia in two patients on three occasions. In the first patient the reaction occurred during the first anaesthetic on propranolol and hydrochlorthiazide medication due to hypertension. Since the major target organ for the anaphylactoid reaction in this patient was the pulmonary circulation, the cardiovascular collapse at his first anaesthetic was misinterpreted as a nonspecific reaction to anaesthesia reinforced by the beta-receptor blocking therapy. At the second anaesthetic central haemodynamics, plasma adrenaline (A) and noradrenaline (NA) were measured. Following injection of thiopentone sudden decreases of mean arterial blood pressure (60%), cardiac output (60%), and systemic vascular resistance (20%) were observed. Thirty minutes later, still during circulatory shock, the concentration of A had increased whereas that of NA was normal. In the second patient the anaphylactogenic drug was supposed to be thiopentone, suxamethonium or alcuronium. In this patient, the fall in arterial blood pressure was associated with bronchospasm and the sudden appearance of peripheral oedema. In both cases initial resuscitation comprised volume replacement and beta 1-agonist therapy but the cardiovascular state was not normalized until vasoconstricting agents were infused.

Cardiovascular effects of enflurane and asphyxia during long-term beta 1-adrenoceptor blockade

The haemodynamic effects of enflurane (1.7% and 3.4% expiratory concentrations) were investigated in sheep (n = 6) pretreated with an infusion of metoprolol (0.2 mg X kg-1 X h-1 for 5 days) and in control animals (n = 6). Chloralose was used as basal anaesthetic. A 90 s apnoea period was included in the experiment to evaluate further the possible side-effects of long-term metoprolol treatment in combination with enflurane anaesthesia. MAC 1.0 for enflurane in the sheep was found at 1.45% end-tidal concentration by separate measurements. Before enflurane administration, the only significant differences between the two groups of animals were a lower systemic vascular resistance and a higher stroke volume during metoprolol treatment. Enflurane abolished these discrepancies in a dose-dependent fashion and similar cardiovascular depression was observed in both groups of animals at 3.4% expiratory concentration of enflurane. Metoprolol did not significantly affect the hypertensive response to apnoea during chloralose anaesthesia alone. At enflurane 1.7% expiratory concentration the apnoea response was small and only the metoprolol-treated animals showed a significant increase in left ventricular end-diastolic pressure. We conclude that 5 days of pretreatment with metoprolol in the sheep model does not significantly impair cardiovascular performance during enflurane anaesthesia.

Vasodilator responses to enflurane in the small intestine

Local effects of enflurane on intestinal vascular resistance were studied in vivo in cats. A jejunal segment was prepared and perfused at constant flow with blood from the femoral arteries. The intestine was either: (1) left with intact sympathetic innervation, (2) denervated and exposed to electrical post-ganglionic vasoconstrictor nerve stimulation, or (3) excluded from neurogenic remote control by post-ganglionic denervation. Enflurane dissolved in lipid and intra-arterially administered to the jejunal segment in doses comparable to those clinically encountered, decreased intestinal vascular resistance in relation to the intra-arterial concentration of the drug. The vasodilator response was, at the highest enflurane doses studied (blood concentration: 400 and 800 mg X 1(-1], most pronounced in the intestine with intact sympathetic innervation. Otherwise, no differences were observed in vasodilator responses between the three different investigated modes of neurogenic influence on the intestine. In vitro enflurane (-in-lipid) did not affect the vasoconstrictor response to electrical field stimulation in the rat mesenteric arterioles. Enflurane, however, dose-dependently reduced spontaneous contractile activity in the rat portal veins.

Intestinal vascular effects of inhaled and locally administered enflurane in the cat

The effects of enflurane on intestinal vascular resistance and blood flow in the intestine were studied in cats during basal chloralose anaesthesia. A jejunal segment was prepared and perfused with blood from both femoral arteries, allowing control of intestinal inflow pressure. Mesenteric venous blood flow was measured with an optical drop recorder. During constant intestinal arterial pressure (75 mmHg; 10 kPa), intestinal vascular resistance was calculated during enflurane inhalation at MAC 0.5 and 1.0 before and after postganglionic denervation of the jejunal segment. Inhalation of enflurane reduced intestinal vascular resistance in a dose-dependent fashion. The decrease in vascular resistance was attenuated but not abolished by post-ganglionic denervation, indicating both peripheral and central nervous sites of action for enflurane. Furthermore, with the intestinal segment perfused at systemic arterial pressure, the effects of locally intraarterially infused enflurane dissolved in a fat emulsion was studied. A vasodilator response was elicited in the intestine when exposed to local arterial enflurane concentrations in the same range as encountered during surgical anaesthesia in man, supporting the hypothesis of a peripheral site of action.

Cardiovascular studies during controlled baroreflex activation in the dog: I. Effects of enflurane

In chloralose-anaesthetized dogs the carotid sinuses were bilaterally perfused with blood from a femoral artery, either at systemic arterial pressure through a direct by-pass or with a pump in order to control the sinus pressure. Influences from cardiac receptors and aortic baroreceptors were eliminated by denervation. Administration of enflurane (1.6% end-tidal concentration) with the presence of barostatic modulation, i.e. the carotid sinuses were perfused at prevailing systemic arterial pressure, reduced cardiac performance (cardiac output, cardiac contractility, heart rate and left ventricular stroke work) and mean arterial pressure. When barostatic compensation of enflurane-induced circulatory changes was prevented by maintaining sinus perfusion pressure constant at the pre-enflurane level, these haemodynamic alterations, with the exception of cardiac output, were significantly more pronounced. Furthermore, systemic vascular resistance decreased. We conclude that barostatic reflexes significantly modify cardiovascular depressive effects of enflurane.

Cardiovascular studies during controlled baroreflex activation in the dog: II. Effects of metoprolol and enflurane

An experimental model was designed to study circulatory drug effects with or without barostatic reflex influences. In dogs anaesthetized with chloralose, both carotid sinuses were perfused from a femoral by-pass either with systemic arterial pressure or with a pump in order to control the sinus pressure. Cardiac and aortic baroreceptors were denervated. I.v. metoprolol (240 micrograms X kg-1 + 102 micrograms X kg-1 X h-1) with constant carotid sinus pressure and thereby constant baroreceptor activation reduced cardiac output, heart rate, cardiac contractility and left ventricular stroke work index. Systemic vascular resistance increased. This response was independent of the degree of baroreflex activation. During the combined administration of enflurane (1.6% end-tidal concentration) and metoprolol, cardiac performance (cardiac output, stroke volume, heart rate, cardiac contractility and left ventricular stroke work index) was depressed independent of the degree of baroreflex activation. Barostatic reflexes, however, counteracted an observed decrease in systemic vascular resistance. This reflex vascular response was, during metoprolol-enflurane administration, associated with an increased left ventricular end-diastolic pressure.

The relationship between circulating catecholamines and ST waveform in the fetal lamb electrocardiogram during hypoxia

Previous studies from this laboratory have shown that changes in the ST waveform in the fetal electrocardiogram are a sign of fetal asphyxia. In the present study, seven chronically instrumented fetal lambs between 117 and 143 days' gestation were studied during 16 one-hour periods of maternally induced hypoxia. The aim was to test the hypothesis of a relationship between the concentration of circulating catecholamines and T-wave amplitude. The response to hypoxia was aged-dependent. Fetuses below 126 days of gestation did not react with electrocardiographic changes and output of epinephrine unless acidosis occurred. In more mature fetuses, hypoxia per se would induce a surge of epinephrine and changes in the ST waveform. Overall there was a strong correlation between the T/QRS ratio and the level of circulating epinephrine. During normoxia, epinephrine was undetectable (less than 0.1 nmol/L) in most fetuses; norepinephrine showed an increase at term. The analysis showed one fetus with chronic changes in the ST waveform (T/QRS ratio greater than 0.30) related to a marked increase in the plasma level of epinephrine in spite of normal blood gas values. These findings complement previous results in the acute and chronically instrumented fetal lamb and suggest that changes in the ST waveform expressed as T/QRS ratio identify a change to anaerobic myocardial metabolism mediated by beta-adrenergic stimulation.

beta-Receptor blockade and neurolept anaesthesia. Withdrawal vs continuation of long-term therapy in gall-bladder and carotid artery surgery

Forty-eight chronically (greater than 3 months) beta-receptor-blocked patients with ischaemic heart disease and/or hypertension were studied on 49 occasions after random distribution to a 4-day, gradual preoperative withdrawal (n = 26) or a continuation (n = 23) of beta-receptor blockers. The patients were scheduled for either a cholecystectomy (n = 28) or a carotid thrombendarterectomy (n = 21) under neurolept anaesthesia. Three patients were excluded from the randomized part of the study due to complications (tachycardia, hypertension, severe angina) after therapy withdrawal. In subgroups, central haemodynamics (beta-receptor blockers withdrawn n = 6, continued n = 8) and creatinine-kinase B (beta-receptor blockers withdrawn n = 9, continued n = 11) were studied. Withdrawal of beta-receptor blockers was associated with high heart rates, supraventricular tachyarrhythmias and a hyperkinetic circulation during pain stimuli. Significantly more postoperative ECG changes (P less than 0.02) indicative of myocardial ischaemia were found than in beta-receptor blocked patients. These patients had low heart rates but also pronounced increases in pulmonary capillary wedge pressures, which in single patients could be associated with myocardial damage. These results imply that beta-receptor blockers should be continued before surgery and that a concomitant vasodilatatory therapy is likely to avoid the drawbacks of an increased cardiac afterload.

Long-term beta-receptor blockade--adrenergic and metabolic response to surgery and neurolept anaesthesia

Twenty-six patients on chronic (greater than 3 months) beta-receptor blocking therapy due to ischaemic heart disease and/or hypertension were randomly distributed to a 4-day gradual withdrawal (n = 13) or a continuation of ordinary therapy until a planned cholecystectomy under neurolept anaesthesia (n = 13). Plasma-adrenaline, -noradrenaline, -potassium, -glycerol, -FFA, -insulin and b-glucose were determined perioperatively. The metabolic response to surgery was as expected with hyperglycaemia and depressed insulin levels, which did not differ significantly between the two groups of patients. Plasma-catecholamines showed the highest mean values during emergence from anaesthesia. Plasma-adrenaline and -potassium were constantly highest in the beta-receptor-blocked patients, who also showed indices of a relatively depressed lipolysis compared to patients in whom beta-receptor blockers had been withdrawn. These discrepancies between withdrawal versus continuation of preoperative beta-receptor blockade seemed to be of small clinical importance and did not oppose the present view that beta-receptor blockers should generally be continued during surgery. However, findings in individual patients suggest that beta-receptor blockade may maintain hypoglycaemia in catabolic patients.

Beta-receptor blocker withdrawal. A preoperative problem in general surgery?

A prospective randomized study was performed in 91 patients scheduled for general surgery on 99 occasions. The patients were chronically (greater than 3 months) treated with beta-receptor blockers because of ischaemic heart disease and/or hypertension and the beta-receptor blockade was either gradually withdrawn (n = 51) during 4 days preoperatively or continued until surgery (n = 48). The effects on arterial blood pressure (BP), heart rate (HR) and rate-pressure product (RPP) at rest and the incidence of chest pain during daily activities were registered. A withdrawal of the beta-receptor blockade was associated with increases of HR (in eight patients greater than 30 beats min-1) and RPP and in patients treated for hypertension there were also increases of systolic and diastolic BP (in five patients greater than or equal to 30/15 mmHg). Patients who continued the beta-receptor blockade until surgery showed no changes. Nine out of 23 patients with a previous history of ischaemic heart disease had an increase of chest pain after withdrawal of the beta-receptor blockers, whereas none of the corresponding 25 patients who continued the therapy suffered from an increased chest pain. Due to the severity of symptoms after beta-receptor blocker withdrawal, surgery had to be postponed in 4 patients. The observations suggest that a 4-day preoperative withdrawal of long-term beta-receptor blockade is potentially hazardous in ischaemic and/or hypertensive patients.

Bupivacaine for intercostal nerve blockade in patients on long-term beta-receptor blocking therapy

Possible cardiovascular side effects of a local anaesthetic in patients on long-term beta-receptor blocking therapy were studied in 26 patients given postoperative intercostal nerve blockades (ICB) with 18-28 ml of plain bupivacaine 0.5% (1.30-1.82 mg kg-1). The patients had a history of hypertension and/or ischaemic heart disease and were scheduled for gall bladder surgery. Thirteen patients were randomized to a gradual preoperative withdrawal of the beta-receptor blockers and the other 13 continued the beta-receptor blockade until surgery. Cardiovascular changes were measured noninvasively and 11 patients were also monitored with pulmonary artery catheters. Blood pressure and heart rate (HR) were stable in all patients although those in whom the beta-receptor blockade was withdrawn had the highest HR and most frequent arrhythmias both before and after ICB. The ICB was associated with a decrease in the overall postoperative arrhythmia incidence, but seemed most efficient (P less than 0.02) concerning the ventricular arrhythmias in the beta-receptor-blocked patients (even including idionodal rhythm). The bupivacaine blood levels did not modify other cardiovascular changes except in one beta-receptor-blocked patient with cardiac failure in whom signs of a slight transient cardiodepression were observed. It is concluded that bupivacaine does not negatively affect cardiovascular stability in long-term beta-receptor-blocked patients. In the presence of cardiac failure, however, an additive cardiodepression may be elicited.

Beta-receptor blockade and spinal anaesthesia. Withdrawal versus continuation of long-term therapy

A prospective study was performed in 43 men scheduled for transurethral resections under spinal anaesthesia. All patients were on chronic beta-receptor blockade because of hypertension and/or ischaemic heart disease. The patients were randomly subjected to either a gradual preoperative withdrawal or a continuation of the beta-receptor blockade. Haemodynamics were measured non-invasively. Spinal anaesthesia was performed and an i.v. injection of atropine given. The patients were then placed in a lithotomy position. Mean anaesthetic level included T6. After beta-receptor blocker withdrawal consistently elevated heart rates, a high incidence of arhythmias, angina pectoris and postoperative ST-T changes indicating myocardial ischaemia were seen. These changes were not seen in patients with continued beta-receptor blockade. Withdrawal of beta-receptor blockers was also associated with an increased total peripheral vascular resistance in connection with spinal anaesthesia. These results suggest that patients on long-term beta-receptor blockade should continue the therapy during and after spinal anaesthesia.